The present invention generally relates to information recording discs and reproducing apparatus therefor, and more particularly to an information signal recording disc which is recorded with information signals including at least video signals and related to a plurality of parallel programs, and a reproducing apparatus for reproducing the recorded information signals from the information recording disc. The information signals have mutually different information contents, and only one of the plurality of parallel programs is selectively reproduced in a given reproducing time period. The information signals are switched in terms of a plurality of fields recorded in one track turn of the information recording disc or in terms of a number of fields smaller than the number of fields recorded in one track turn of the information recording disc, and are time-sequentially recorded on the information recording disc together with predetermined codes. In the present specification, those programs only one of which is reproduced in a given reproducing time period, are referred to as parallel programs.
Information recording discs such as video discs are put into various use. The information recording disc may be recorded with a plurality of programs so that only one of the plurality of programs is selectively reproduced in a given reproducing time period. In a case where the information recording disc is used for a simulation game of golf or automobile racing, for example, it is necessary to selectively reproduce one of a plurality of recorded programs related to a plurality of possible results as the game progresses, depending on the speed and direction of the golf swing, the direction of the wind and the like in the case of the golf game, or depending on the manner in which the driver operates the steering wheel, the accelerator, the brake and the like in the case of the automobile racing game. In such a case, the plurality of programs related to the plurality of possible results or possible processes are recorded on a conventional information recording disc in independent blocks, and an arbitrary program is selectively reproduced by making a random access search to a corresponding block. However, it takes a time in the order of at least one second to complete the random access search, and there is a disadvantage in that the player (operator) will lose interest in the game when it takes such a long time for the game apparatus to react to a manipulation made by the player's.
Accordingly, an information recording disc in which the above described disadvantages are overcome, was previously proposed in a U.S. patent application Ser. No. 523,668 filed Aug. 15, 1983 in which the assignee is the same as the assignee of the present application. According to this previously proposed information recording disc, information signals at least including video signals are recorded at a rate of a plurality of fields in one track turn of the information recording disc. The information signals related to a plurality of parallel programs are switched in terms of the plurality of fields recorded in one track turn on in terms of a number of fields smaller than the number of fields recorded in one track turn, and are time-sequentially recorded on the information recording disc. When continuously reproducing an arbitrary program from the information recording disc, it is possible to obtain a normal reproduction picture and normal reproduction audio signals by forcibly shifting (hereinafter referred to as kicking) a reproducing element in a track width direction. In addition, it is possible to instantaneously change to a different program so as to obtain a normal reproduction picture and normal reproduction audio signals of this different program, by not carrying out the kick. Therefore, the previously proposed information recording disc is advantageous in that the recorded information signals related to the plurality of parallel programs are reproduced in real-time, and it is possible to prevent the player from losing interest in the game due to slow reaction of the game apparatus.
However, in the previously proposed information recording disc, a program which is being reproduced is changed from one program to another program by not carrying out the kick. For this reason, it is only possible to change the program which is being reproduced from one program to another program which is recorded in continuance with the one program. As a result, there is a disadvantage in that it is possible to instantaneously change the program which is being reproduced to an arbitrary program in a case where three or more parallel programs are recorded in the information recording disc.
Accordingly, a reproducing apparatus for reproducing the recorded information signals from the information recording disc was proposed in a Japanese Patent Application No. 58-137266 in which the applicant is the same as the assignee of the present application, in order to elimate the disadvantages of the previously proposed information recording disc. The previously proposed reproducing apparatus controls a pulse generating circuit for generating pulses (kick pulses) which are used to kick the reproducing element, based on a difference between a program number which is presently being reproduced and a program number which is to be reproduced, which program numbers are assigned to each of the plurality of programs recorded on the information recording disc. According to the previously proposed reproducing apparatus, it is possible to change from one program to another program even at an arbitrary reproducing point when there are three or more parallel programs from which an arbitrary program may be reproduced. For this reason, the program which is being reproduced can be changed to another program including those parallel programs which are not recorded in continuance with the program which is being reproduced. Therefore, the program which is being reproduced can be changed to an arbitrary program out of a large number of parallel programs. Thus, in a case where the previously proposed reproducing apparatus plays an information recording disc which is used for a game, the parallel programs will be reproduced in real-time and the player will be able to make a selection out of a large number of possible selections, and the game will become more interesting for the player.
However, the plurality of parallel programs from which the arbitrary program is to be selected and reproduced, are not recorded over the entire recording surface of the information recording disc. Parallel program recorded regions in which the plurality of parallel programs are recorded and single program recorded regions in which only a single program is recorded, coexist on the information recording disc. In addition, even within one parallel program recorded region, the number of parallel programs recorded in one sector may be different from the number of parallel programs recorded in another sector. In other words, the number of parallel programs recorded in one sector of one parallel program recorded region may be different from the number of parallel programs recorded in another sector of the same parallel program recorded region, depending on the progressing state of the game and on the needs. But since the previously proposed reproducing apparatus plays the information recording disc in which the number of parallel programs and the codes within the address signal indicative of the program number are not determined according to a unified method, there is a disadvantage in that it is impossible to continuously reproduce a parallel program recorded region and a single program recorded region in an optimum state. In addition, when the number of parallel programs changes during the reproduction, there is a disadvantage in that it is impossible to carry out a continuous reproduction by instantaneously changing to a desired program. Furthermore, as the reproducing element of the previously proposed reproducing apparatus moves to the single program recorded region from the parallel program recorded region, the real-time it takes for the reproducing element to reach the single program recorded region is not constant because a scanning locus of the reproducing element differs depending on the parallel program which is selectively reproduced from among the plurality of parallel programs.